1. Field of the Invention
The present invention relates to controlling operation of a passenger-operated machine such as a lawn mower, tractor, snow plough or the like, in general to render the machine inoperable when the operator is unseated. More particularly, the invention relates to an operation controlling apparatus wherein whether the operator is seated or not seated is detected by a seat detecting means whose output maintains a disabled state of the machine until the apparatus assumes a start waiting state; and, the disabled engine state is assumed only after the operator is unseated for more than a predetermined time period.
2. Prior Art
Operation controlling apparatus for engine-driven passenger-operated machines such as lawn mowers, tractors and the like are disclosed, for example, in the following patents.
U.S. Pat. No. 4,051,915--Behrens discloses an interlock circuit for a tractor which prevents starting unless the transmission is in neutral and the power take-off is disengaged, and also prevents the tractor from being driven when the parking brake is engaged. A first switch detects the neutral status of a variable speed transmission. Another switch detects the disengaged state of the power take-off clutch. A further switch detects the released (operating) state of the parking brake. The engine can be operated only when all the noted switches are disposed in their respective detecting states. The presence of the operator on the seat is not detected, and accordingly the engine is not stopped when the operator is unseated.
U.S. Pat. No. 4,317,500--Bening discloses a safety start and shutdown device for a vehicle having an electrically activated power take-off. The disclosed device disables the power take-off clutch when the operator is not seated, as detected by a seat switch, and also disables starting or operation of the engine. The device detects the neutral state of the variable speed transmission such that the engine cannot be started or the power take-off engaged when the vehicle is in gear.
Devices according to the foregoing description are inconvenient in that the engine may be stopped automatically whenever the operator rises from the seat, even instantaneously as caused for example when the operator bounces on the seat when operating the vehicle over an uneven surface. To overcome this problem a safety interlock can be provided with a timer circuit arranged to delay response to the "ON" and "OFF" positions of the instantaneous seat switch.
This arrangement allows the operator to be supported comfortably on the seat in a stable and high position, even though this arrangement is more prone to bouncing of the operator relative to the seat support. The seating switch also can be arranged outside of the seat (between the seat support and the chassis rather than between the operator and the seat support) to be less sensitive to bouncing of the operator relative to the seat. However such a switch is less sensitive to whether the operator is indeed seated. In this case, even when the engine ought to be stopped due to unseating of the operator as mentioned above, the seat switch cannot stop the engine automatically. A switch disposed outside the seat often will repeatedly turn "ON" and "OFF" momentarily due to vibration induced motion. The engine produces a vertical oscillation of the seat support relative to the seat switch, and the seat switch responds to the oscillating weight of the seat rather than to the weight of the operator. Therefore it is necessary that special consideration be give to the weight of the seat and the resilient means supporting it.